Zusammenfassung: Web architectures are an important asset for various large-scale web applications, such as social networks or e-commerce sites. Being able to handle huge numbers of users concurrently is essential, thus scalability is one of the most important features of these architectures. Multi-core processors, highly distributed backend architectures and new web technologies force us to reconsider approaches for concurrent programming in order to implement web applications and fulfil scalability demands. While focusing on different stages of scalable web architectures, we provide a survey of competing concurrency approaches and point to their adequate usages.

Zusammenfassung: State-machine replication (SMR) enables transparent and delayless masking of node faults.
It can tolerate crash faults and malicious misbehavior, but usually comes
with high resource costs, not only by requiring multiple active replicas,
but also by providing the replicas with enough resources for the expected peak load.
This paper presents a vertical resource-scaling solution for
SMR systems in virtualized environments, which can dynamically adapt
the number of available cores to
current load. In similar approaches, benefits of CPU core scaling
are usually small due to the inherent sequential execution of SMR systems in order to achieve determinism.
In our approach, we utilize sophisticated deterministic
multithreading to avoid this bottleneck and experimentally demonstrate that
core scaling then allows SMR systems to effectively tailor resources
to service load, dramatically reducing service provider costs.

Zusammenfassung: For preserving privacy, blockchains can be equipped
with dedicated mechanisms to anonymize participants. How-
ever, these mechanism often take only the abstraction layer of
blockchains into account whereas observations of the underlying
network traffic can reveal the originator of a transaction request.
Previous solutions either provide topological privacy that can
be broken by attackers controlling a large number of nodes,
or offer strong and cryptographic privacy but are inefficient
up to practical unusability. Further, there is no flexible way to
trade privacy against efficiency to adjust to practical needs. We
propose a novel approach that combines existing mechanisms to
have quantifiable and adjustable cryptographic privacy which is
further improved by augmented statistical measures that prevent
frequent attacks with lower resources. This approach achieves
flexibility for privacy and efficency requirements of different
blockchain use cases.

Mödinger, David; Kopp, Henning; Kargl, Frank; Hauck, Franz J.

Towards Enhanced Network Privacy for Blockchains

Short research statement for the DSN Workshop on Byzantine Consensus and Resilient Blockchains (BCRB)

Juni
2018

Zusammenfassung: Privacy aspects of blockchains have gained attention
as the log of transactions can be view by any interested party.
Privacy mechanisms applied to the ledger can be undermined by
attackers on the network level, resulting in deanonymization of
the transaction senders. We discuss current approaches to this
problem, e.g. Dandelion, sketch our own approach to provide
even stronger privacy mechanisms and discuss the challenges
and open questions for further research in this area.

Zusammenfassung: Tinnitus is a common medical condition which interfaces many different disciplines, yet it is not a priority for any individual discipline. A change in its scientific understanding and clinical management requires a shift toward multidisciplinary cooperation, not only in research but also in training. The European School for Interdisciplinary Tinnitus research (ESIT) brings together a unique multidisciplinary consortium of clinical practitioners, academic researchers, commercial partners, patient organizations, and public health experts to conduct innovative research and train the next generation of tinnitus researchers. ESIT supports fundamental science and clinical research projects in order to: (1) advancing new treatment solutions for tinnitus, (2) improving existing treatment paradigms, (3) developing innovative research methods, (4) performing genetic studies on, (5) collecting epidemiological data to create new knowledge about prevalence and risk factors, (6) establishing a pan-European data resource. All research projects involve inter-sectoral partnerships through practical training, quite unlike anything that can be offered by any single university alone. Likewise, the postgraduate training curriculum fosters a deep knowledge about tinnitus whilst nurturing transferable competencies in personal qualities and approaches needed to be an effective researcher, knowledge of the standards, requirements and professionalism to do research, and skills to work with others and to ensure the wider impact of research. ESIT is the seed for future generations of creative, entrepreneurial, and innovative researchers, trained to master the upcoming challenges in the tinnitus field, to implement sustained changes in prevention and clinical management of tinnitus, and to shape doctoral education in tinnitus for the future.

Zusammenfassung: The increased use of mobile devices has led to an improvement in the public health care through participatory interventions. For example, patients were empowered to contribute in treatment processes with the help of mobile crowdsourcing and crowdsensing technologies. However, when using the latter technologies, one prominent challenge constitutes a continuous user engagement. Incentive management techniques can help to tackle this challenge by motivating users through rewards and recognition in exchange of task completion. For this purpose, we aim at developing a conceptual framework that can be integrated with existing mHealth mobile crowdsourcing and crowdsensing platforms. The development of this framework is based on insights we obtained from the TrackYourTinnitus (TYT) mobile crowdsensing platform. TYT, in turn, pursues the goal to reveal insights to the moment-to-moment variability of patients suffering from tinnitus. The work at hands presents evaluated data of TYT and illustrates how the results drive the idea of a conceptual framework for an incentive management in this context. Our results indicate that a proper incentive management should play an important role in the context of any mHealth platform that incorporates the idea of the crowd.

Zusammenfassung: Smartphones have become an integral part in life of users, mainly because over the course of recent years, they have become extremely mainstream, cheap, flexible, and they pack high-end hardware that offers high computational capabilities. Many, if not all of today’s smartphones are equipped with sophisticated sensors which enable smart mobile sensing. The programmable nature of these sensors in the smartphones enable a wide array of possibilities to achieve user-centric or environmental sensing. Even though there have been different approaches proposed to develop a smartphone app, platform, design frameworks, APIs, and even application-specific architectures, there is a lack of generalised referenceable architecture in the literature. In this paper, we propose a generic reference architecture, which can be derived to create more concrete mobile sensing or mobile app architectures. Furthermore, we realise the proposed reference architecture in a healthcare use case, specifically in the context of applying smart mobile sensing to support tinnitus research.

Zusammenfassung: Surveys indicate that users are often afraid to entrust data to cloud storage providers, because these do not offer sufficient privacy. On the other hand, peer-2-peer–based privacy-preserving storage systems like Freenet suffer from a lack of contribution and storage capacity, since there is basically no incentive to contribute own storage capacity to other participants in the network.
We address these contradicting requirements by a design which combines a distributed storage with a privacy-preserving blockchain-based payment system to create incentives for participation while maintaining user privacy. By following a Privacy-by-Design strategy integrating privacy throughout the whole system life cycle, we show that it is possible to achieve levels of privacy comparable to state-of-the-art distributed storage technologies, despite integrating a payment mechanism.
Our results show that it is possible to combine storage contracts and payments in a privacy-preserving way. Further, our system design may serve as an inspiration for future similar architectures.

2016

Hauck, Franz J.; Habiger, Gerhard; Domaschka, Jörg

UDS: a novel and flexible scheduling algorithm for deterministic multithreading

Zusammenfassung: The actor model is an established programming model for distributed applications. Combining event sourcing with the actor model allows the reconstruction of previous states of an actor. When this event sourcing approach for actors is enhanced with additional causality information, novel types of actor-based, retroactive computations are possible. A globally consistent state of all actors can be reconstructed retrospectively. Even retroactive changes of actor behavior, state, or messaging are possible, with partial recomputations and projections of changes in the past. We believe that this approach may provide beneficial features to actor-based systems, including retroactive bugfixing of applications, decoupled asynchronous global state reconstruction for recovery, simulations, and exploration of distributed applications and algorithms.

2009

IEEE International Conference on Internet Multimedia Systems Architecture and Application

Bangalore, India

Dezember
2009

Zusammenfassung: The globalisation of our society leads to an increasing need for spontaneous communication. However, the development of such applications is a tedious and error-prone process. This results from the fact that in general only basic functionality is available in terms of protocol implementations and encoders/decoders. This leads to inflexible proprietary software systems implementing unavailable functionality on their own. In this work we introduce Instant-X, a novel component-based middleware platform for multimedia applications. Unlike related work, Instant-X provides a generic programming model with an API for essential tasks of multimedia applications with respect to signalling and data transmission. This API abstracts from concrete component implementations and thus allows replacing specific protocol implementations without changing the application code. Furthermore, Instant-X supports dynamic deployment, i.e., unavailable components can be automatically loaded at runtime. To show the feasibility of our approach we evaluated our Instant-X prototype regarding code complexity and performance.

Zusammenfassung: We present Virtual Nodes, a framework to provide fault-tolerance for grid applications by replicating them over multiple nodes. For the performance of replicated systems it is crucial that the application characteristics and load pattern are taken into account when the replication protocol is selected. For that reason Virtual Nodes offer a wide variety of configuration parameters that allow to fine-tune framework properties to optimise the overall system performance.

Schmidt, Holger; Elsholz, Jan-Patrick; Hauck, Franz J.

Instant-X: a component-based middleware architecture for a generic multimedia API